Oil fired conversion assembly



June 10, 1969 R. E. SHENBERGER 3,448,736

OIL FIRED CONVERSION ASSEMBLY Filed Jan. 10, 1968 INVENTOR. ROBERT E.SHENBERGER A TTORNEYS United States Patent US. Cl. 126-116 3 ClaimsABSTRACT OF THE DISCLOSURE A furnace conversion assembly for convertinga gas fueled furnace into an oil fueled furnace. A hollow walled,combustion chamber box includes a header on one side adapted to fit ontothe gas burner header opening of a gas furnace heat exchanger. Air inletholes in the box permit passage of air through the hollow walls of thebox. An air outlet for the hollow walls is provided adjacent a flueleading into the interior or combustion chamber of the box. Air drawnthrough the hollow walls of the box is combined with fuel oil in an oilburner for combustion of the oil and air mixture within the interior ofthe chamber box, the oil burner being mounted to the combustion chamberbox. Combustion products are directed through the header and into thegas furnace heat exchanger to exhaust in the normal manner through theheat exchanger.

Background of the invention This invention relates to a furnaceconversion assembly for converting a gas fueled furnace into an oilfueled furnace and, more particularly, to a conversion assembly whichmay be readily attached to various existing gas furnaces with a minimumof modification.

It is well known that gas furnaces are very desirable, and thuscurrently are especially popular as a means for heating residences.However, it often happens that public utilities are unable to providenatural gas service for many homes in many areas. For this reason, it issometimes necessary to use alternate fuels such as coal, which isunderstandably not a desirable fuel for residential heating, or oil,which is a desirable fuel for residential heating.

Rather than being required to build a separate furnace model for eachtype of fuel, it has been found advantageous to utilize a basic designfurnace for use with either oil or gas. Thus, an installation may bechanged after it is in service, or an installation may be originally setup for either gas or oil depending upon the desires of the customer.

Summary of the invention In a principal aspect the present invention isa furnace conversion assembly for converting a gas fueled furnace intoan oil fueled furnace. The original gas fueled furnace is of the typewhich includes a heat exchanger with a gas burner header for receivinggas burners leading into the heat exchanger. The conversion assemblycomprises an enclosed combustion chamber which is surrounded by a shroudso that an air space is defined between the chamber and the shroud. Airis made to flow in this air space and is drawn off to be combined withfuel oil in the oil burner. The oil and air mixture subsequentlycombusts in the chamber with the combustion products passing from thecombustion chamber, through the header opening in the furnace and intothe heat exchanger of the furnace. The air passing through the hollowspace betwen the chamber and the shroud serves to insulate thecombustion chamber while simultaneously being heated to more eflicientlycombust with the fuel oil.

It is thus an object of the present invention to provide an improvedfurnace conversion assembly.

Patented June 10, 1969 It is a further object of the present inventionto provide a furnace conversion assembly for converting a gas fueledfurnace into an oil fueled furnace.

One other object of the present invention is to provide an economicallymanufactured conversion assembly which can be incorporated with existinggas furnaces with a minimum of expense, time and effort.

Still another object of the present invention is to provide a conversionassembly which insures more efiicient operation of the furnace and morecomplete combustion of the fuel.

These and other objects, advantages and features of the presentinvention will be more fully set forth in the detailed description whichfollows:

Brief description of the drawings In the detailed description whichfollows, reference will be made to the drawing comprised of thefollowing figures:

FIG. 1 is a cut-away perspective view of a typical residential gasfurnace including the oil conversion assembly of the present inventionwith a fuel oil burner mounted thereon;

FIG. 2 is a perspective view of the convention assembly of theinvention;

FIG. 3 is a top plan view of the assembly illustrated in FIG. 2;

FIG. 4 is a front end view of the assembly shown in FIG. 2;

FIG. 5 is a cross-sectional view taken substantially along the line 55of FIG. 3; and

FIG. 6 is a cross-sectional view of the assembly taken substantiallyalong the line 6-6 of FIG. 4.

Description of the preferred embodiment FIG. 1 illustrates a typical gasfurnace unit which includes the oil conversion assembly of the presentinvention. The gas furnace is enclosed in a cabinet 12. Air enters atthe bottom of cabinet 12 and passes through the air filter 14 beingdrawn therethrough by a squirrel cage fan 16 which is driven by anelectric motor 18.

The cool, inlet air is forced up through an opening 20 in a Wall 22which defines the lower boundry of a heat exchanger cavity within thecabinet 12. The heat exchanger cavity is defined by the outside walls ofthe cabinet 12, the bottom cavity wall 22 and a back cavity wall 24. Aheat exchanger 26 is fastened within the heat exchanger cavity so thatthe air passing up through the opening 20 may circulate about the heatexchanger 26, be heated and pass through the plenum 28 to duct workin'the residence. The walls of the heat exchanger cavity are preferablyinsulated to insure that the air remains heated as it passes into theresidence duct work.

The heat exchanger 26, as utilized in the gas furnace, includes a lowerburner portion 30 with header opening 32 passing through the back cavitywall 24. In a gas furnace, gas burners are inserted through the headeropening 32 into the burner portion 30. The gas is ignited and combustedwith air within the burner portion 30. The combustion products then risethrough the remainder of the heat exchanger 26 and pass out through anexhaust vent 34.

To convert the gas fuel furnace to an oil fueled furnace, a conversionassembly 36 of the present invention is positioned in the header opening32 in place of the gas burners which are removed. An oil burner 38 withappropriate controls is mounted on the assembly 36. The oil burner 38includes a motor and fan assembly 40 which draws air into the burner 38for mixture with fuel oil. The air and fuel oil mixture is then forcedthrough the oil burner gun which projects into the interior of theassembly 36. There the vaporized mixture is ignited. The combustionproducts then pass from the assembly 36 through the header opening 32and into the burner portion 30 of heat exchanger 26 to heat air flowingthrough the heat exchanger cavity in the same manner air is heated bythe gas furnace.

Referring now to FIGS. 26, there is shown in greater detail theconversion assembly 36 of the invention. The conversion assembly 36gene-rally has the shape of a rectangular parallelepiped. It includes aheader 42 adapted to fit into the header opening 32. The header 42includes two openings 44 and 45 leading from the interior of theassembly 36. The number of openings in the header 42 is equal to thenumber of cells in the furnace. Thus one or more openings may be definedin the header, depending upon the configuration and construction of theheat exchanger.

Combustion products are expelled through these header openings 44 and 45into the burner portion 30 of the head exchanger 26. Preferably theheader 42 is fabricated from a fire resistant asbestos composition andprojects partially into the header opening 32 to insure that thecombustion products are directed into the heat exchanger 26.

The assembly also includes an inner chamber 48 and a shroud '50 whichsurrounds the chamber 48. The shroud 50 is spaced from the chamber 48 toprovide a hollow air space between the shroud 50 and the chamber 48. Abrace and separator member 52 maintains the shroud 50 in a fixedposition in relation to the chamber 48. A plurality of air openings 54are defined in the brace 52. A single air outlet 56 is defined in thetop of the shroud 50. A fan housing assembly 58 is attached to theshroud 50 and extends upward from the air outlet 56. Included within thefan housing assembly 58 is a conventional air flow damper or shutter 60which is manually controlled.

A burner inlet mounting tube 62 passes through the shroud 50 and chamber48, and provides a passage to the interior of chamber 48. As may be seenby examining FIG. 1, the gun of the oil burner 38 passes through thetube 62 into the interior of the assembly 36. The burner 38 is mountedon the tube 62 and held in position by suitable means such as bolts 64shown in FIG. 1.

The throud '50 includes flanges 66 and 67 adjacent the header 42. Theflanges attach to the back cavity wall 24 and serve to hold the assembly36 in contact with the furnace by fastening bolts passing through theflanges 66 and 67.

In operation, the fan and burner assembly 38 of the oil burner cause airto be drawn through the air openings 54. This air passes around thehollow walls of the assembly 36 and through the outlet 56. The heatedair is then combined with fuel oil in the burner 38 and ignited aspreviously described. Since the chamber 48 is fabricated from sheetmetal and conducts heat readily, air passing between the chamber 48 andthe shroud 50 becomes heated prior to combustion with oil. Moreover,since the air passes around the chamber 48, it acts as insulation forthe furnace. In addition, since the air is heated before it is combinedwith the fuel oil, the air and fuel mixture provides a more efficientand complete combustion. Thus, there are two effects achieved by thepresent construction; first, the air insulates the combustion chamber,and second, the air is preheated to provide a more efficient cornbustionwith the oil.

There are numerous other advantages to a construction of this type. Forexample, it is no longer necessary to manufacture two distinct types ofheat exchanger to burn both oil and gas. In addition, blower and motorsizes can be reduced by utilizing a combination as presently claimed. Aswill be noted, the gas-fired heat exchanger is a multicell clam-shelltype compared to a drum and wrap-around radiator type heat exchangerwhich is quite common on oil-fired furnaces. The multi-cell clam-shelltype of heat exchanger oflers less resistence to air flow than the drumand radiator type. Thus a smaller motor is required to drive the oilburner since there is less air flow resistance. Consequently, theoperating efiiciency of the conversion assembly of the invention isimproved in relation to many standard oil-fired furnaces. This increasein efficiency is due to the insulating and preheating effects previouslydescribed and has resulted, in tests run by the inventor, in increasedefficiencies as high as 9%.

While there has been set forth a preferred embodiment of the presentinvention, it is to be understood that all those embodiments obvious topersons skilled in the art and all those embodiments equivalent to theclaimed subject matter are to be included within the scope of theappended claims.

What is claimed is:

1. A furnace conversion assembly for converting a gas fueled furnaceinto an oil fueled furnace, said furnace including a heat exchanger witha gas burner header opening in one side thereof, said furnace alsoincluding an oil burner, said assembly comp-rising in combination:

an enclosed combustion chamber, said chamber including a header servingas an exit for combustion products passing from said chamber to saidheat exchanger, said header being attached to said header opening, saidchamber also including a burner inlet mounting tube, said tube includingmounting means for mounting said oil burner to combust an oil and airmixture within said chamber, and

a shroud surrounding said chamber and providing an enclosed air spaceabout said chamber, said shroud including a plurality of openings toadmit air in said air space, said shroud also including a single airexit duct, said duct being positioned adjacent said inlet tube so thatair drawn through said air space and directed from said duct passes intosaid oil burner to mix and combust with said oil.

2. The assembly of claim 1 including air flow control means within saidair exit duct.

3. The assembly of claim 1 wherein said shroud and chamber comprisesubstantially rectangular sided parallelepipeds, with one of said sidesdefining said header, said air space openings being defined about theouter periphery of the bottom of said assembly, and said air exit ductand said inlet tube being positioned on top of said assembly with airpassing around said assembly to insulate said chamber and provide morecomplete combustion.

References Cited UNITED STATES PATENTS 2,267,905 12/1941 Frantz 126-116X 3,266,550 8/1966 Sick et al 43l238 X 3,382,862 4/1968 Martz 126ll6 XJAMES W. WESTHAVER, Primary Examiner.

US. Cl. X.R.

